People have been encouraged to wear homemade fabric masks in public where social distancing is not possible, newly updated World Health Organisation (WHO) advice states.

The WHO previously stressed there was no evidence that wearing a mask – whether medical or other types – by healthy people in the wider community could prevent them from infection with respiratory viruses, including Covid-19.

However, it said “evolving” new science now pointed to the use of medical-grade masks in hospital settings – even for those not treating coronavirus patients – as well as similar protection worn by people aged 60 or over, or with underlying health conditions, when outside of their home where social distancing was not possible.

The comments came as Health Secretary Matt Hancock announced all hospital visitors and outpatients will be required to wear face coverings and all hospital staff will be required to wear surgical masks in England from June 15.

The Government previously said face coverings would be mandatory on public transport, but, again, only from June 15.

Speaking during a virtual press briefing, WHO director-general Dr Tedros Adhanom Ghebreyesus said: “In areas with widespread transmission, the WHO advises medical masks for all people working in clinical areas of a health facility, not only workers dealing with patients with Covid-19.

“Secondly, in areas with community transmission, we advise that people aged 60 years or over, or those with underlying conditions, should wear a medical mask in situations where physical distancing is not possible.

“Thirdly, the WHO has also updated its guidance on the use of masks by the general public in areas with community transmission.

“In light of evolving evidence, the WHO advises that governments should encourage the general public to wear masks where there is widespread transmission and physical distancing is difficult, such as on public transport, in shops or in other confined or crowded environments.”

He said new research suggested fabric masks should consist of “at least three layers of different material” in order to be effective.

But Dr Tedros also cautioned against an over-reliance on face masks, and said every country’s “best defence” was to implement an effective test, trace and isolate system.

He said: “I cannot say this clearly enough: masks alone will not protect you from Covid-19.

“Masks are not a replacement for physical distancing, hand hygiene and other public health measures.

“Masks are only of benefit as part of a comprehensive approach in the fight against Covid-19.

“The cornerstone of the response in every country must be to find, isolate, test and care for every case, and to trace and quarantine every contact.”

Dr Maria Van Kerkhove, the WHO’s Covid-19 technical lead, said the organisation’s updated guidance on face masks was based on “new, novel research that we didn’t have a month ago”.

She said people could source fabric materials at home to make a mask, the inner layer being an absorbent material such as cotton, a middle layer of non-woven material to act as a filter, and an outer layer of a non-absorbent material such as polyester.

Dr Van Kerkhove said: “With those three layers, and in that combination, that fabric can actually provide a mechanistic barrier, that if someone were infected with Covid-19, it could prevent those droplets from going through and infecting someone else.”